Three-dimensional conformal radiotherapy (3D CRT) holds promise of potentially improving the outcome in prostate cancer without an increase in the morbidity. This proposal seeks support as a member of a multi-institutional group to carry out a dose escalation study for treatment of the prostate cancer through 3D CRT and to collect three dimensional dosimetric distribution data so that partial normal tissue tolerance can be established. The University of Chicago Center for Radiation Therapy has developed a number of planning tools and has used these to treat over 750 patients with 3D CRT techniques. Specific aims are a) to develop protocols for Phase I, II, and III studies, b) recommend specific treatment parameters to the multi-center working group to carry out such trials, c) enter patients into the protocol, and d) collect image, volume of interest, dosimetric, toxicity, and response data for transmission to the national operations and statistics center for analysis. Through a multi-center cooperative group mechanism, a new maximum tolerated dose will be established. Key considerations of our proposal include a) use of objective criteria (PSA and transrectal ultrasound) to identify locally advanced patients for the study b) contribution of a significant number of African Americans into the study population c) a proposal to the working group to define margins based on transrectal ultrasound and PSA findings d) utilization of advanced 3D treatment planning software e) software tools to determine the mobile target volume and accuracy of portal placement using image correlation software, f) monitoring of toxicity, and g) and monitoring of response using serial PSA measurements.